The present invention is directed to minimizing loss of iodine from an iodophor solution, notably polyvinylpyrrolidone iodophor, which is stored within a packaging. More specifically, the present invention is directed to a method for minimizing this loss, and to the packaging provided therefor, in which a certain minimal level of additional iodide is provided, in addition to the iodophor solution, which prevents or minimizes leaching of iodine through the packaging itself.
Combination of elemental iodine and certain organic polymers, e.g., polyvinylpyrrolidone and detergent polymers, have been termed iodophors. The organic polymers used to form an iodophor comprise a broad range in molecular weight and chain length, and may be either ionic or non-ionic in character, as well as possessing either surfactant or non-surfactant properties. A loose bond forms between the iodine and organic polymer to form a complex. Aqueous solutions of up to about 30% in iodine content, may be prepared.
The general method for the preparation of a iodophor complex is to bring into intimate contact, elemental diatomic iodine with the selected polymer, either in the dry or powder form or in the presence of a suitable solvent. Heat may be used to accelerate complex formation. Upon completion of the reaction, the iodophor complex of the respective polymeric carrier with iodine is obtained in certain reproducible proportions of one to the other.
Iodophor preparations are described in terms of available or titratable iodine which is considered to be the iodine released from the complex to exert germicidal action thereof. However, such available iodine determinations do not reflect either the total iodine content of the iodophor, or its germicidal potency. The iodine moiety of polyvinylpyrrolidone (povidone)-iodine complex is present in an aqueous iodophor solution in the form of different thermodynamically stable anionic iodine species and diatomic iodine. The anionic iodine forms are capable of generating diatomic iodine in the course of their respective equilibrium reactions. The anionic species do not distribute themselves into an extracting solvent which removes only the nonionic iodine. Such iodine is generated in the course of the iodine equilibrium reaction and extraction thereof by a solvent fractionates the equilibrium state. The disturbed equilibrium reaction is soon re-established to restore new anionic iodine species, but now at a different concentration level since the previous aqueous iodine content of the solution has been reduced by the extracting solvent.
Since the iodophor iodine exerting microbicidal action exists in solution in dynamic equilibrium with ionic iodine species, removal of one or more of the iodine species results in formation of new equilibrium forms. An extracting solvent removes or consumes iodine from the iodophor solution in a manner similar to that of a microbial and organic load during degerming use of the iodophor solution. The amount of iodine available for germicidal action in an iodophor preparation therefore is the amount of iodine in equilibrium in the solution at the time of use. Such equilibrium iodine content represents the germicidal potency of the preparation, but not the total iodine content titrated for the preparation nor the apparent distribution of the iodine forms. Although iodophor solutions have been assayed in the art for available or titratable iodine, it is the equilibrium iodine which is the particular form of iodine present in the iodophor solution that is instantly available to exert microbicidal action. This form of iodine differs from titratable iodine and the other iodine species present in the iodophor solution. Therefore, the equilibrium iodine content of an iodophor solution is to be distinguished from its titratable iodine content.
The titratable iodine content of an iodophor preparation includes the iodine reservoir of the iodophor preparation (povidone iodine), as well as the equilibrium iodine in solution: EQU Titratable iodine=Reservoir Iodine+Equilibrium Iodine
However, it is the equilibrium iodine alone that exerts the microbicidal action of the preparation at any given moment. The portion of the titratable iodine content remaining after subtracting the amount of equilibrium iodine present, serves as the iodine reservoir to generate new equilibrium iodine in solution as it is consumed by the microbial and bio-organic load in the course of microbicidal activity, but does not exert such germicidal action by itself.
Povidone-iodine (polyvinylpyrrolidone-iodine or PVP-I) USP (U.S. Pharmacopeia) is the raw material used in the preparation of all PVP-I containing formulations. Povidone-iodine is a complex of iodine with povidone. It contains not less than 9.0% by weight, and not more than 12% by weight of available-iodine (titratable iodine) calculated on a dry basis. Povidone Iodine USP has a specification for iodide ion of not more than 6.6% by weight on a dry basis.
The level of iodide ions inherently present in any PVP-I formulation using PVP-I raw material, therefore depends on the amount of iodide ion present in the raw material PVP-I used. For example, on a theoretical basis, if the PVP-I contains 6% by weight iodide ion, then a formulation containing 10% by weight of PVP-I would contain 0.6% by weight iodide ion. However, PVP-I raw material containing a level of iodide ion greater than specifications of the U.S. Pharmacopeia, could also be used in formulating a PVP-I containing product.
Thus, the minimum amount of iodide ion inherently present in a PVP-I formulation could be as low as 0.0% by weight, while the maximum amount of iodide ion inherently present in such a PVP-I formulation would be the amount contributed by the PVP-I raw material used to formulate the same. For example, on a theoretical basis, if a formulation contains 0.36% by weight PVP-I, and the PVP-I contains the maximum iodide allowable of 6.6% by weight, then the formulation will have 0.0237% by weight iodide present.
Iodophor solutions, notably povidone-iodine, have been packaged for medicinal use, e.g. in soft plastic bottles or containers which can be used for various medicinal purposes, e.g. douching. However, a severe problem that has been encountered with such packaged iodophor solutions, is that elemental iodine (equilibrium iodine) has leached through the packaging itself. This has resulted both in a decrease in stability and medicinal capacity of the iodophor solution contained within the packaging, and has also made it difficult to handle such packaging since the elemental iodine which has leached therethrough causes staining and burning if touched.
However, it has now been surprisingly found that separate introduction of additional iodide, above and apart from the iodide already present in the noted iodophor solution, actually reduces and even totally eliminates the leaching of any elemental iodine from the iodophor solution through the packaging.